Build: Bump multidict from 6.7.1 to 6.9.1 (#4117)

Bumps [multidict](https://github.com/aio-libs/multidict) from 6.7.1 to 6.9.1.
- [Release notes](https://github.com/aio-libs/multidict/releases)
- [Changelog](https://github.com/aio-libs/multidict/blob/master/CHANGES.rst)
- [Commits](aio-libs/multidict@v6.7.1...v6.9.1)

---
updated-dependencies:
- dependency-name: multidict
  dependency-version: 6.9.1
  dependency-type: indirect
...

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